Adsorption-based CO 2 capture has enjoyed considerable research attention in recent years. Most of the research efforts focused on sorbent development to reduce the energy penalty. However, the use of suitable gas−solid contacting systems is key for extracting the full potential from the sorbent to minimize operating and capital costs and accelerate the commercial deployment of the technology. This paper reviews several reactor configurations that were proposed for adsorptionbased CO 2 capture. The fundamental behavior of adsorption in different gas−solid contactors (fixed, fluidized, moving, or rotating beds) and regeneration under different modes (pressure, temperature, or combined swings) is discussed, highlighting the strengths and limitations of different combinations of gas−solid contactor and regeneration mode. In addition, the estimated energy duties in published studies and current technology readiness level of the different reactor configurations are reported. Other aspects, such as the reactor footprint, the operation strategy, suitability to retrofits, and the ability to operate under flexible loads are also discussed. In terms of future work, the key research need is a standardized techno-economic benchmarking study to calculate CO 2 avoidance costs for different adsorption technologies under standardized assumptions. Qualitatively, each technology presents several strengths and weaknesses that make it impossible to identify a clear optimal solution. Such a standardized quantitative comparison is therefore needed to focus on future technology development efforts.

No abstract

This paper reports the experimental demonstration of the novel swing adsorption reactor cluster (SARC) concept in a multistage fluidized bed reactor with inbuilt heat-transfer surfaces for postcombustion CO2 capture at a capacity up to 24 kg-CO2/day. SARC employs combined temperature and vacuum swings (VTSA), driven by heat and vacuum pumps, to regenerate the solid sorbent after CO2 capture. The laboratory-scale reactor utilized a vacuum pump and a heating oil loop (emulating the heat pump) to demonstrate 90% CO2 capture from an N2/CO2 mixture approximating a coal power plant flue gas fed at 200 NL/min. In addition, dedicated experiments demonstrated three important features required for the success of the SARC concept: (1) the polyethyleneimine sorbent employed imposes no kinetic limitations in CO2 adsorption (referred to as carbonation) and only minor nonidealities in regeneration, (2) a high heat-transfer coefficient in the range of 307–489 W/m2 K is achieved on the heat transfer surfaces inside the reactor, and (3) perforated plate separators inserted along the height of the reactor can achieve the plug-flow characteristics required for high CO2 capture efficiency. Finally, sensitivity analysis revealed the expected improvements in CO2 capture efficiency with increased pressure and temperature swings and shorter carbonation times, demonstrating predictable behavior of the SARC reactor. This study provides a sound basis for further scale-up of the SARC concept.

This paper presents the first experimental demonstration of the novel swing adsorption reactor cluster (SARC) for post combustion CO 2 capture. The SARC concept combines a temperature and vacuum swing for sorbent regeneration. A heat pump is used for transferring heat from the exothermic carbonation reaction to the endothermic regeneration reaction. Sorbent regeneration under vacuum allows for a small temperature difference between carbonation and regeneration, leading to a high heat pump efficiency. This key principle behind the SARC concept was demonstrated through lab-scale experiments comparing combined vacuum and temperature swing adsorption (VTSA) to pure temperature swing adsorption (TSA), showing that a 50 mbar vacuum can reduce the required temperature swing by 30-40 °C. A complete SARC cycle comprising of carbonation, evacuation, regeneration and cooling steps was also demonstrated. The cycle performed largely as expected, although care had to be taken to avoid particle elutriation under vacuum and the CO 2 release rate was relatively slow. The SARC principle has therefore been successfully proven and further scale-up efforts are strongly recommended.

No abstract

New process concepts, such as the swing adsorption reactor cluster (SARC) CO2 capture process, are often techno-economically investigated using idealized modeling assumptions. This study quantifies the impact of this practice by updating a previous economic assessment with results from an improved reactor model validated against recently completed SARC lab-scale demonstration experiments. The experimental comparison showed that the assumption of chemical equilibrium was valid, that the previously employed heat transfer coefficient was conservatively low, and that the required reduction of axial mixing could be easily achieved using simple perforated plates in the reactor. However, the assumption of insignificant effects of the hydrostatic pressure gradient needed to be revised. In the economic assessment, the negative effect of the hydrostatic pressure gradient was almost canceled out by deploying the experimentally observed heat transfer coefficients, resulting in a small net increase in CO2 avoidance costs of 2.8–4.8% relative to the unvalidated model. Further reductions in axial mixing via more perforated plates only brought minor benefits, but a shorter reactor enabled by the fast experimentally observed adsorption kinetics had a larger positive effect: halving the reactor height reduced CO2 avoidance costs by 13.3%. A new heat integration scheme feeding vacuum pressure steam raised from several low-grade heat sources to the SARC desorption step resulted in similar gains. When all improvements were combined, the optimal CO2 avoidance cost was 23.7% below the best result from prior works. The main uncertainty that needs to be overcome to realize the great economic potential of the SARC concept is long-term sorbent stability: mechanical stability must be improved substantially and long-term chemical stability under real flue gas conditions must be demonstrated.

No abstract

No abstract